Transient signal direction finder



N. nu@

er, QV

June 27, 1950 w. J. KEssLER Er Al.

'IRANsIENI SIGNAL DIRECTION FINDER Filed Jan. 12, 194s NN U63 ok iatented .lune 27,- Y

,iss

N. Y., assignors to the Board of Commissioners of State Institutions of the State of Florida Application January 12, 1948, Serial No. 1,788

4 Claims.

The present invention relates to transient signal direction finders.

This application is a continuation-impart of our application Serial No. 777,416, led October 2, 1947, for Direction Finder, now abandoned.

In order to locate atmospheric disturbances, as well as to obtain a bearing on any radio transmitter, it has been customary to provide a direction finding apparatus comprising loop antennae arranged in planes normal to each other, together with the necessary circuits whereby an impulse received on the antennae will appear as a trace on a cathode ray tube screen.

One difculty in the use `of the above-described apparatus arises from the fact that there may be slight dierences in the components of the amplifying circuits which are provided between each antenna loop :and the cathode ray tube. As a result, the circuit including one loop may not be tuned like the other circuit, or one circuit may produce an output signal which is not in phase with the output signal of the other circuit. Either situation results in an inaccurate indication on the cathode ray tube screen.

Objects of the present invention are to provide a direction finder including means to permit testing and adjustment of the circuits to maintain their output signals in phase with each other and also to permit each circuit to be properly tuned.

Other `objects and advantages of the invention Will be apparent from the accompanying drawing and following specification wherein:

Figure 1 is a diagram of a circuit including the present invention, and

Figure 2 diagrammatically illustrates the direction nder and particularly the loops and cathode ray tube or oscilloscope.

Figure 2 indicates the usual type of direction linding antenna l including a north-south loop Il :and an east-West loop l2. These loops are respectively connected to the circuits hereinafter described, by :a suitable cable I3 leading to a control cabinet generally designated M. An os-f cilloscope unit l5 is included in the cabinet I4.

As is customary in the operation of such an apparatus, the loops Il and I2 lie in vertical planes at right angles to each other with the north-south loop oriented in those directions. In the event an atmospheric disturbance creates static at a point I6 directly northeast of the antenna IU, the resultant electromagnetic radiation Will act upon the loops II and I2 along the line I1, i. e., along la line which is at lan angle of 45 to both loops. With the screen I5 provided with protractor markings, the resultant signal imposed on the apparatus will cause the cathode bearri normally appearing :at the point l-B on the screen to be shifted s-o that la line I9 will appear on the screen. This line is formed by the rapidly moving cathode ray beam and indicates the true direction of the atmospheric disturbance from the station. impressed upon the loops II and I2 acts upon the deflecting plate ofthe cathode ray tube to thereby deflect the cathode beam from its normal position indicated at I8 to form the line i9. An apparatus of the type under discussion is usually tuned to some low frequency of the order of 10 kilocycles in order to provide a reasonable Voltage output as well as selectivity and to eliminate interference from low frequency commercial code stations.

The actual voltage output of a tuned antenna is not a replica of the static crash but, instead, is a damped sinusoidal wave. If the damped waves from the two loops are amplified without distortion, or at least with identical distortion, a sharp, straight line will appear at I9 on the oscilloscope I5. i

The damped lwaves from the two loops must be amplified without distortion, or with identical distortion, in order to produce la sharp line on the cathode ray tube. Otherwise, the desired sharp line will not appear on the oscilloscope screen but, instead, a distorted elliptical line will appear, making it very difficult to determine the oompass direction that the line is supposed to indicate. "Dhe present invention includes means to permit adjustment of the various components of the amplifying circuits so that both circuits willv produce output signals which are in phase. It also permits the amplifying circuits to be correspondingly tuned for optimum results.

Referring now to Figure l, this figure diagnammatically illustrates the amplifying means used with the apparatus of Figure 2 for the purpose of amplifying the signals received on the :antenna I0. As is diagrammatically illustrated in Figure l, the north-south loop il will be connected' to the input end or left-hand end of the upper circuit 2| illustrated in Figure 1 while the east-west loop I2 `will be connected to the left-hand end of the lowermost circuit 22 of the gure. The amplifying circuit for each loop is identical and, therefore, Figure l completely illustrates only the cir-cuit 2| which is connected to the north-south loop ll. Such portions of the amplifying circuit 22 connected to loop I2 :as are omitted from `Figure l .are identical with the corresponding portions ofthe circuit 2l illustrated in the upper It will be understood that the ,voltagel the reference characters used in connection with that circuit terminate in the.y letter -Vf., 'Ifhe circuit 22 of theeast-West loop I2 controls the horizontal deflection platesoff'tubel and the reference characters of the latter circuit "the fore terminate in the letter"II`l-"""(S.ueh'refer A characters as do not terminate ineither'bfthe letters V or I-I refer to parts notu'sedin bothYV circuits.

Referring to the circuit 2|, the output of the loop is connected toy the amplifying circuit iff-through a' socket so lvf 1 Thefipjbeig an i'r'i'liict'an'ce, the voltage which it appliesfttlie amplifying circuitl may be increased by tuning thefflop'to resonanceat thedesired frequency by" operation of condenser zC V mounted across the loop. A resistor RS Vis also mounted across the loop and in parallel with the condenser QIV. The purpose ofthisresistor is 'to' providfan adjustment whereby thef'operator can givetlietwo loops identical characteristics. Vlt vwill be, understood 'that the provision of a variableres'i vr suchas 133V across 'thevoutput of eachloop'cifIf-f,l cuit will enable their fQ value. to be 'suitably matched.' As "is'well known,l the" Q',"'r"fQ talug, @,f 'a tuned Circuitii'a. measure of. the Sharp?.

ness of tuning. Y-It usually is defined sthe'ratio of inductive reactance to series resistancejfat re'sonanfc'efor as ratiojof Ashunt resistance toinf. ductivejreactance. i

' 'I he'` loop output is coupled to a vacuum tube :i

circuit of the cathodef'coupled 'type ydesi'gnated VIV." This Circuit gives Stability anderer/ents.. the tubeffrom loading'the high impedanc loop` circuit In addition, the. 10st impe-*dah 'jtl tof'V theY cathode upledfcircuit re Shift- "LIn, therworss th tiibeVLV Co. aideviceto Q0ui2le-the1f00pitother mai' vine.' lments. "Of' the" amplify' C 2 l` The' amount of' coupling can be v -arl adiusiifg. resistor 35V; Becausethe @e 'teY 'Q'f the loop will be. grounded',l 'only'vfhalf"offthejvolt age'dvelopedby the loop is'. applied to VJV.

YIV. gives avoltage 'amplificatori dfslishflxlessr mani, The grid resistor'fn'aviislargeit,'ofiiy functionbeingtoprevent'the grid'freinbe7 ing completehr free from ground if,v the loop. isbpe.. ,f Y.. Y Y, From VIV, the signal goes to twocontacts of4 a group 'SGVof xed contacts. Group SGV isljone ofthree groups of contacts, the othefitwom'groups beingy 'designated' SGO and` YSrClI-I, vllfjSIe.ctively.y A S will be hereinafter explained, eachofff'these, three groups has associated'therewith a moving. contact forming part of. a'gang switch so 'thatA all of the' contactscan be. operated together'. "'In' the normaloperation ofthefapparatus, the moving contact CV associatedwitljicontac't Agroifi'p'. SGV. will be in the position illustrated in lig;V u'regi.' As a result.' the signa frofnvl'v. Willits. carried to'the grid of,r tube VZV-forming part'ofA theresistancel'couple,amplification stage. This.

stage serves "as the gain controll'for the ampli` frthe gain being controlled. by v'aryingfthe Cei gdeibiaS-j Resistor, Ewig. the.. Kamm?.

*condenser C|3V make up the tuned circuit.

time@ if; both 'ci vent phase d and provides a variable positive voltage on the cathode. In order to prevent VZV from ever operating at high bias,V cathode resistor RBV provides a small amount of self bias. Condenser'. CBV is adjustable to correct phase shifts in the stage including VZV. VCondenser CSV and the corresponding condenser in the horizontal plate amplifying circuit 22 provide an infinite number of possible combination of setting'swhich will produce the required phase characteristics. However, best operation is obtained by having the smallesty possible. Valuerof capacitance. Therefore, one of thesev two condensers should be set tominimum and theA required adjustment made with the other.

" From-`theresistance-coupled stage including tunedfamplication. The tube in this stage pro-Y videsthe amplification and the inductor LIV and As 11.1 .the Gase. 0f .the .tened 109D @Hiwit this tuned circuitV must'be provided'with-"ieans for adjustcuit.y 'VIfhis vis accompaniedf'by a "high Variable valueof shunt res tanefafffordedby the resistor Ril 8V. f' YIt' beobserved` that vcon'denser-'`C"| '3Vv is"A in yshint 'with-the"`""ut`put` ofY AV3X?v and that Y R |'8`V is'i'n Yparallel'vvitl'rthe Variable condenser justinentioned. The stage o'fmtunegd rma .the Sage. @keine vof esigenti is th'ehapglied toatita Si Cer .egual-ed .S cluding'- tube VdV and transfer 1en'l'flV;

Ive. Plates.ith?afir"Qt'vefigalgqeictii platesjinithe Cathode. 'mv tube. .l .The Y e'cted acrossA the seconda serves.' aftrim ng maniiiacturing :wie agg ,v 'The remai d ing'portion jfi'tnls iS partielle Q11 theplatesof.

ficati'n provides additional select'vityoyer-t' t Y and, during such tests, place them in properly tuned relation and correct for differences in phase, the two circuits 2I and 22 are adapted to be connected through a socket S03 to an oscillator, not shown. The oscillator, as Well as afbuffer tube, notshown, are connected in the circuits 2I and 22 by operation of the ganged moving contacts CV, CO, and CH. As has been stated above, moving contact CV is associated with a group of xed contacts SGV associated with the vertical deflection plate circuit 2 I. Moving contact CO is associated with the group SGO of xed contacts associated with the oscillator circuit and moving contact CH is associated with the group SGH of fixed contacts associated with the circuit 22 which amplifies the current delivered t the horizontal deflection plates of the oscilloscope I5. The manner of connecting the group of contacts SGO and the corresponding moving contact CO to the oscillator is illustrated in Figure 1.

It will be observed that a resistance network R23, R24 and R25 is provided to provide attenuation of the calibration oscillator signal during the testing or alignment of the apparatus.

Each group of xed contacts includes six contacts designated I to Il. As has been stated above, when the moving contacts CV, CO and CH are in the position illustrated in Figure 1, i. e., in engagement with contact 3 of the respective groups, the apparatus is in normal operation to transmit a signal received on the antenna I0 to the oscilloscope I5.

When it is desired to test the amplifying circuits, the oscilloscope beam would be adjusted until a small spot appears at the center of the oscilloscope screen, lall amplifier gain controls then being set at minimum value. Then the oscillator would be energized to the desired frequency. The gang switch contacts CV, CO and CI-I would then be moved into engagement with the contact 6 of each group of fixed contacts. With the moving contacts in this position, the oscillator signal will be fed only to the horizontal amplifier circuit 22. The horizontal tuning control on the oscilloscope would then be adjusted until the horizontal trace on the oscilloscope screen is at a maximum.

Then the ganged moving contacts would be moved to engage the xed contact in each group of contacts SGV, SGO and SGH. In this position, the oscillator output will be delivered to the vertical plate circuit 2| for the oscilloscope. The tuning control for these plates would then be adjusted until the resultant vertical trace on he oscilloscope screen is approximately the same as that which was obtained for the horizontal trace in the preceding test. Without moving the ganged contacts, the output paralleling switch SW2 will then be closed and the transformer phasing condensers C I "IV and CI'IH would be adjusted until the resulting elliptical trace on the oscilloscope screen becomes a straight line. Should maximum capacitance on one of these phasing condensers .and minimum capacitance on the other phasing condenser fail to produce a straight line trace, a iixed condenser may be placed in parallel with one of the condensers CI 'IV or CI iH. When a satisfactory straight line trace has been obtained, indicating that the output of the two transformers is in phase, switch SW2 will be opened.

Operation of the moving contacts of the ganged switch to respectively engage the contacts 4 of the groups of xed contacts will result in the oscillator output being delivered to both of the amplier circuits 2l and 22 in parallel. The tuning,

phasing and gain of the circuits 2i and 22 can then be tested, in that order, until the resulting tra-ce on the oscilloscope screen is .a straight line inclined at an angle of 45 (as at I9 in Figure 2) over a large range of frequencies. There is a slight interaction between the three adjustments mentioned but the net result of the adjustments should provide a straight line trace of 45 on the screen.

With the moving contacts of the gang switch now moved to engage contact I of each group of xed contacts, the oscillator signal will be fed toloops I I and I2 but the output of only loop I.I will be delivered to its amplifying circuit. The loop tuning condenser C IV can then be adjusted until a maximum vertical trace is obtained. By varying resistor RSV, the tuning can also be further adjusted. The result of this adjustment should be to obtain a maximum vertical trace consistent with contemporary static conditions in the atmosphere.

A further test is obtained by shifting the moving contacts to engage the fixed contact 2 of each group. In this position, the oscillator signal will be fed to both of the loops iI and I2 butonly the output of the loop I2 will be delivered to its amplifying circuit. Adjustment of condenser CIH will give maximum horizontal trace. The purpose is to obtain a horizontal trace approximately the same size as 4'the vertical trace obtained with the immediately preceding test.

The moving contacts of the gang switch may then be restored to the position illustrated in Figure l, i. e., in engagement with the Xed contact 3 of each group. However, with the oscillator still in operation, the oscillator signal will -be fed to both loops and each amplifying circuit 2I and 22 will be connected to its loop. Any tendency of the trace toward an elliptical form can then be corrected by a slight adjustment of one of the tuning condensers CIV or CI H. The difference in tuning or Q of the loops can be adjusted at this time by closing the output paralleling switch SW2. One of the loop gain controls may be adjusted until the resulting straight line trace is at 45.

The oscillator can now be turned off with the gang switch left at position :3' and the equipment should be ready for normal operation and observation.

The terminology used in the specication is for the purpose of description and not of limitation, the scope of the invention being indicated in the following claims.

We claim:

l. In a transient signal direction finder, a pair of loop antennae, an amplifying circuit for each of the respective antennae, an oscilloscope, the output of each amplifying circuit being connected to the respective pairs of deecting plates of said oscilloscope, an oscillator, means for attenuating the signal of said oscillator, means for selectively connecting said oscillator to the input of either and both of said amplifying circuits and simultaneously disconnecting said circuits from said loops, and adjustment means for matching the tuning and phase of said amplifying circuits over the entire transmission frequency-range of the direction finder.

2. The invention as defined in claim l, Wherein said adjustment means includes a variable condenser and a variable resistor across each loop at the input end of the amplifying circuit connected thereto, a transformer associated with asias@ ah of 'Said amplifier circuitsjeachtransformer h ngits' primar-y in -the last stage of the c'orf responding amplier circuit, the secondaries `of the transformers being'connected to the respective pairs .of deflection'plates of said oscilloscope, 'and a. Variable condenser -across'the secondary of each-transformer.

f3.-In a transient signal ldirection nder, a-pair of Aloop antennae, an amplifying circuit foreach of "the respective'fantennae, ari-oscilloscope, the -iitbut of leach amplifying circuit being connectedt'o the respective pairs of deecting -platesr'of y"said oc'sillocsope an oscillator, meansfor atten- VHating"the signal fof vsaid oscillator, means for lsel'e'c'tiv'ely connecting lsaid oscillator -to the -in- 'put'iof either land vbotlfi of said amplifying circuits and v`simultaneously disconnecting said circuits 'from -safid'loo'ps means for selectively connecting 'said'os'cillator to either 'and both of said loops, .and -Fadjustmenit means or matching the tuning :and phase of said amplifying circuits-over rthe f entire 'transmission frequency-range of the `direcz tion finder. l

L4. The-invention'as dened in fclaim f3, .wherei'n said adjustment means 'includesx-a variable condenser and a *variableV resistor Yacross each '.loopvat ith'e input end of the `.amplifying circuit connected thereto, a transformer Aassociated with i each 'of said amplifier circuits, each transformer @having -its Eprimary in the 'laststage :of .the icoryrespipndirig' amlier circuit, the ys'ec'zlonda-ries-of =the1-transformersbeing connected to Athe respectivepairs ofdeection plates of said oscilloscope, and "la variable v4condenser across the secondary of each transformer. Y

' l J. KEssLER.

"O VID GANO.

CHARLES A. MORENO. v

REFERENCES ,CITED @he Yfollowing references are of record in the 'fiieofthis patent: L

UNITED sTArrEs PATENT-rs 

